As part of my One Switch 100 book (well behind schedule, but no surprise there), I have a short section on exploration with a single switch in video games.

Proteus by Ed Key and David Kanaga is first to go in. It's a beautiful game of freedom with little to no pressure. You can explore with complete independence with one-switch if you can understand the auto-scanning system. If not, you can use two switches, one-controlled by a helper and the other by the explorer.

UPDATE: seems to work with the least trouble on a 64-bit Win 7 or Win 8 machine. Have a fix for 32-bit though.... Not all switch interfaces pass through an event 1:1 (see here with an adapted impact switch interface which is 1:1). Presently the Tecla Shield can't be used with this system very well as it has some lag and forces a quick down-up activation of any control it is linked to. The nice people at Komodo Open Lab are looking into this though.